Senator Charles Schumer, Democrat of New York, has recused himself from reviewing Comcast’s agreement to buy Time Warner Cable after the revelation that his brother, the lawyer Robert Schumer, worked on the deal.

Mr. Schumer, who sits on the Senate Subcommittee on Antitrust, Competition Policy and Consumer Rights, praised the merger of the country’s two largest cable giants in a statement on his website on Thursday. On Friday, the magazine American Lawyer named Robert Schumer of the law firm Paul, Weiss, Rifkind, Wharton & Garrison its “dealmaker of the week” for his work on the transaction.

On Monday, Mr. Schumer’s office said that the senator would recuse himself from having any oversight of the deal, the largest acquisition of 2014.

“As Senator Schumer and his brother had never discussed the matter before, the piece in American Lawyer was the first Senator Schumer learned that his brother had worked on the deal,” Matt House, a spokesman for Charles Schumer, said in a statement. “Now that he’s aware of his brother’s involvement, Senator Schumer will recuse himself from Congressional consideration of the matter to avoid any appearance of bias.”

But the website LittleSis — which describes itself as a “grassroots watchdog network connecting the dots between the world’s most powerful people and organizations — continued to raise issues about the relationship on Tuesday.

“Schumer’s claim that he was unaware of his brother’s involvement is surprising in light of Robert Schumer’s decades-long relationship with Time Warner Cable,” the website wrote on Tuesday. “He has been the company’s go-to M&A lawyer for years, winning public accolades along the way.”

That relationship, according to LittleSis, includes:

Helping to represent Warner Communications in its merger with Time Inc. in 1989 (Time Warner spun off Time Warner Cable in 2009).

Taking on Time Warner as a client when Peter Haje, a partner at Paul Weiss, left to work for the company in 1992

Various articles in American Lawyer magazine praising Mr. Schumer’s work on various Time Warner deals

Robert Schumer was also on the “Power Lawyers” list in 2011, and the current Time Warner Cable chief, Rob Marcus, praised his work on previous deals involving the company.

On Thursday, Mr. Schumer’s office issued a news release in which the senator was quoted saying that he expected that the “results of the merger will be positive for New York.”

When asked about the connections between Robert Schumer and Time Warner on Tuesday, Mr. House reiterated that Charles Schumer had “no knowledge his brother was working on the deal.”

Comcast’s plan to acquire its largest rival has raised several antitrust questions, and many lawmakers have already pledged to scrutinize the impact to consumers as some analysts have questioned whether federal regulators will block the deal.